The present invention relates to an improvement in a silicon oxide film, and a method of forming a silicon oxide film as well as a parallel-plate remote plasma enhanced chemical vapor deposition apparatus for depositing a silicon oxide film over a rectangular shaped substrate, and more particularly to a silicon oxide film reduced in content of hydroxyl group materials, and a method of forming a silicon oxide film reduced in content of hydroxyl group materials as well as a parallel-plate remote plasma enhanced chemical vapor deposition apparatus for uniformly depositing a silicon oxide film reduced in content of hydroxyl group materials over a rectangular shaped substrate with a large area.
The silicon oxide films are used in various semiconductor devices, for example, a gate insulation film of a field effect transistor, an inter-layer insulator, a field oxide film and a passivation layer covering the semiconductor device as well as a passivation layer used during fabrication processes of the semiconductor device. The silicon oxide film may be formed in a thermal oxidation method, a low pressure thermal chemical vapor deposition method and a plasma chemical vapor deposition and an atmospheric pressure thermal chemical vapor deposition method, and a sputtering method. In the chemical vapor deposition method, a silicon source gas such as monosilane (SiH4), disilane (Si2H6), and TEOS (Si(OC2H5)4) and an oxygen source gas are fed to a reaction chamber for causing a reaction at a relative low temperature in the range of 300-600xc2x0 C. with an assist with a thermal energy and a plasma energy to form a silicon oxide film. For those reasons, the CVD silicon oxide films are often used in the semiconductor devices.
The CVD silicon oxide film is likely to include or capture hydroxyl group materials such as water H2O and silanol Sixe2x80x94OH. Such the hydroxyl group materials cause deteriorations in electric properties and characteristics and also deteriorations in reliability of device operation and performance as well as in reliability of device process. If the CVD silicon oxide film is used as the gate insulation film, then those deteriorations are serious problems.
The reasons why the CVD silicon oxide film is likely to include the hydroxyl group materials such as water H2O and silanol Sixe2x80x94OH are that the hydroxyl group materials are likely to be generated by the reaction of the source gases and also that if the silicon oxide film is porous and has a low film density, then waters are likely to be captured in the pores of the silicon oxide film. The hydroxyl group materials such as silanol Sixe2x80x94OH are structurally incorporated in the silicon oxide film, for which reason the hydroxyl group materials cause deteriorations in electric property and characteristic and reliability as insulator. It is possible to prevent pore-sites of the silicon oxide film from capturing water by covering a layer over the silicon oxide film. However, the hydroxyl group materials are generated by the reaction of the source gases, for which reason it is difficult to prevent the generation of the hydroxyl group materials. As a silicon source gas, monosilane (SiH4), disilane (Si2H6), and TEOS (Si(OC2H5)4) are available which include hydrogen atoms. If such the silicon source gas is reacted with an oxygen source gas, then the hydroxyl group materials are generated. Further, when the silicon oxide film is deposited by the plasma enhanced chemical vapor deposition method, hydrogen radicals are formed whereby the generation of the hydroxyl group materials is promoted. As a result, the content of the hydroxyl group materials in the silicon oxide film is increased. TICS (Si(NCO)4) free of hydrogen is also available as a silicon source gas. The silicon oxide film made from TICS (Si(NCO)4) is inferior for practicing the semiconductor device.
The silicon oxide films deposited by the chemical vapor deposition method using reaction of monosilane with oxygen-containing gas have been studied and developed, wherein a reduction in content of the hydroxyl group materials in the silicon oxide film.
In Applied Physics Letters, vol. 60, No. 2, pp. 198, it is disclosed that the increase in substrate temperature in the low pressure thermal chemical vapor deposition using monosilane and oxygen gas results in reduction in the content of the hydroxyl group materials in the silicon oxide film. This method of mere increase in substrate temperature is not effective for reduction in the content of the hydroxyl group materials in the silicon oxide film unless the substrate temperature is risen to not less than 600xc2x0 C. This method of increasing the substrate temperature to not less than 600xc2x0 C. is inapplicable to when the silicon oxide film is deposited over a glass substrate or when the silicon oxide film is deposited on a metal interconnection layer of a low melting point.
In Japanese laid-open patent publication No. 62-190760, it is disclosed that monosilane, carbon dioxide gas (CO2) and nitrogen gas (N2) are used as source gases to form a silicon nitride oxide film by the plasma enhanced chemical vapor deposition method thereby reducing the content of the hydroxyl group materials in the silicon nitride oxide film. Such a CVD silicon nitride oxide film is available for inter-layer insulator and passivation film. If the CVD silicon nitride oxide film is formed as a gate insulation film on a silicon layer or a silicon substrate, an interface state density is higher than when the gate insulation film comprises the silicon oxide film on the silicon substrate or the silicon layer.
In Journal of Vacuum Science and Technology, vol. 4, No. 3, pp. 681, there is disclosed a remote plasma enhanced chemical vapor deposition method which settles the problem like that hydrogen radicals promote generation of the hydroxyl group materials in the silicon oxide film. Only oxygen source gas is supplied or oxygen source gas and inert gas are supplied for causing a plasma thereby generating oxygen radicals so that the oxygen radicals are diffused toward the substrate and further a silicon source gas which is electrically neutral is fed in the vicinity of the substrate, whereby the silicon source gas is reacted with the oxygen radicals, without generating hydrogen radicals, to form a silicon oxide film by the plasma chemical vapor deposition. This remote plasma chemical vapor deposition method does not suppress a reaction of monosilane with oxygen source gas which generates the hydroxyl group materials. Namely, the remote plasma chemical vapor deposition method does not settle the problem with generation of the hydroxyl group materials in the silicon oxide film.
In the above Journal of Vacuum Science and Technology, it is also disclosed that the gas injector for injecting monosilane gas is circularshaped. If this gas injector is used for depositing a silicon oxide film over a rectangular-shaped glass substrate which is often used for a liquid crystal display device, then a further problem is raised with non-uniformity of the silicon oxide film or variation in thickness of the silicon oxide film over position. This problem is remarkable when the rectangular-shaped substrate has a large size.
In IEEE Electron Device Letters, vol. 15, No. 2, pp. 69, it is disclosed that a parallel-plate remote plasma chemical vapor deposition apparatus is applicable to a large size substrate, wherein an intermediate mesh plate electrode and a silicon source gas injector are provided so that an oxygen plasma generation region is separated in space from a silicon source gas injection region and the substrate.
In Japanese laid-open patent publication No. 5-21393, it is disclosed that, in the parallel-plate remote plasma enhanced chemical vapor deposition apparatus, the silicon source gas injector is provided in the vicinity of the intermediate mesh plate electrode in order to attempt to uniformly deposit of the silicon oxide film over the large size substrate as illustrated in FIG. 1. The parallel-plate remote plasma chemical vapor deposition and the intermediate mesh plate electrode as well as monosilane gas injector are cylindrically shaped as illustrated in FIG. 2. This parallel-plate remote plasma chemical vapor deposition apparatus is applicable but only to the circular-shaped substrate and thus inapplicable to the rectangular-shaped substrate which is often used for the liquid crystal display device.
In the above circumstances, it had been required to develop a novel silicon oxide film with a reduced content of the hydroxyl group materials, and a method of forming a novel silicon oxide film with a reduced content of the hydroxyl group materials as well as a parallel-plate remote chemical vapor deposition apparatus capable of uniform deposition of a silicon oxide film over a rectangular-shaped substrate.
Accordingly, it is an object of the present invention to provide a novel silicon oxide film free from the above problems.
It is a further object of the present invention to provide a novel silicon oxide film with a reduced content of the hydroxyl group materials.
It is a still further object of the present invention to provide a novel silicon oxide film with excellent electrical properties and characteristics.
It is yet a further object of the present invention to provide a novel silicon oxide film with high reliability as an insulator.
It is a further more object of the present invention to provide a novel method of forming a silicon oxide film free from the above problems.
It is still more object of the present invention to provide a novel method of forming a silicon oxide film with a reduced content of the hydroxyl group materials.
It is moreover object of the present invention to provide a novel method of forming a silicon oxide film with excellent electrical properties and characteristics.
It is another object of the present invention to provide a novel method of forming a silicon oxide film with high reliability as insulator.
It is still another object of the present invention to provide a parallel-plate remote chemical vapor deposition apparatus free from the above problems.
It is yet another object of the present invention to provide a parallel-plate remote chemical vapor deposition apparatus capable of uniform deposition of a silicon oxide film over a rectangular-shaped substrate.
It is further another object of the present invention to provide a remote chemical vapor deposition apparatus free from the above problems.
It is an additional object of the present invention to provide a remote chemical vapor deposition apparatus capable of uniform deposition of a silicon oxide film over a rectangular-shaped substrate.
The present invention provides a silicon oxide film having a ratio of A1 to A2 which is not higher than 0.21, where A1 is a first peak integrated intensity of a first peak belonging to Sixe2x80x94OH and appearing in the vicinity of a wave-number of 970 cmxe2x88x921, and A2 is a second peak integrated intensity of a second peak belonging to Oxe2x80x94Sixe2x80x94O and appearing in the vicinity of a wave-number 820 cmxe2x88x921, and each of the first and second peak integrated intensities is defined as a product of peak width at half height and a peak height of a Raman spectrum obtained by a Raman scattering spectroscopic analysis of the silicon oxide film.
The present invention also provides a chemical vapor deposition method comprising the step of depositing a silicon oxide film, wherein a ratio of a first flow rate Fo of oxygen gas to a second flow rate Fsi of a silicon source gas is not lower than 20.
The above and other objects, features and advantages of the present invention will be apparent from the following descriptions.